This invention relates to stabilizer compositions comprising degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said products including a free mercaptan. This invention also relates to polymer compositions containing a polymer normally susceptible to heat-induced deterioration and the degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said products including a free mercaptan. It also relates to such polymer compositions further containing a metallic-based heat stabilizer. This invention also relates to articles of manufacture, e.g. pipe, film, and window profile, made from stabilized polymer compositions containing a polymer normally susceptible to heat-induced deterioration, the degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said-based heat stabilizer. Another aspect of this invention is the development of a novel reaction scheme which, although crude, affords latent mercaptans which need no purification to be highly active PVC heat stabilizers at low use levels.
This invention also relates to latent mercaptans which are substantially free of the offensive odor typical of mercaptans and which may be used as anti-oxidants, odorants, anti-microbial agents, chelating agents and photostabilizers; and as intermediates for the preparation of anti-oxidants and primary heat stabilizers. It also relates to such anti-oxidants and primary heat stabilizers.
It is well known that the physical properties of various organic polymers deteriorate and color changes take peace during processing of the polymer and during exposure of formed polymer products to certain environments. The prime examples of polymers which are susceptible to degradation during processing are the halogen-containing polymers such as the vinyl and vinylidene polymers in which the halogen is attached directly to carbon atoms. Poly(vinyl chloride) or PVC, copolymers of vinyl chloride and vinyl acetate, and poly(vinylidene chloride), the principal resin in self-clinging transparent food wraps, are the most familiar polymers which require stabilization for their survival during fabrication into pipes, window casings, siding, bottles, and packaging film, etc. When such polymers are processed at elevated temperatures, undesirable color changes often occur within the first 5 to 10 minutes as well as during later stages of the processing. Haziness, which sometimes accompanies the color changes, is particularly undesirable where clear products are needed. The addition of heat stabilizers to such polymers has been absolutely essential to the wide-spread utility of the polymers. From a great deal of work in the development of more and more effective heat stabilizers there has emerged two principal classes: organotin compounds and mixed metal combinations. Organotin-based heat stabilizers are the most efficient and widely used PVC stabilizers. Synergistic combinations of alkyltin mercaptides and free mercaptans are particularly efficient heat stabilizers for PVC during extrusion. They have not been entirely satisfactory, however, because of several failings on the part of the mercaptan synergist. Many mercaptans give off an offensive odor even at room temperature and the odor grows worse at PVC processing temperatures. The oxidative stability of the mercaptans is very often very poor. Oxidation of the free mercaptans diminishes the synergism. Thus, a combination having an enhanced synergism would be welcomed by the PVC industry. Also, because of the end-use of articles made from some polymers, many polymeric compositions require the presence of both biocides and heat stabilizers but the use of the organotin mercaptide/mercaptan combination in such a composition is often frustrated by the tendency of the free mercaptan to deactivate a biocide such as the much used OBPA (10,10xe2x80x2-oxybisphenoxarsine).
In U.S. Pat. No. 3,660,331, Ludwig teaches the stabilization of vinyl halide resins by certain thioethers and thioesters of tetrahydropyran. Better heat stabilizer compositions are still needed, however. The thioethers of this invention satisfy that need.
It is an object of this invention, therefore, to provide a heat stabilizer composition having the synergy of a mercaptan plus improved oxidative stability.
It is another object of this invention to provide a latent mercaptan-containing heat stabilizer composition which is substantially free from the offensive odor typically associated with mercaptans.
It is a related object of this invention to provide a latent mercaptan-containing heat stabilizer composition which has a decidedly pleasant odor.
It is a further object of this invention to provide .n improved polymeric composition containing a biocide and a latent mercaptan-containing heat stabilizer.
It is a related object of this invention to provide a polymeric composition containing a heat stabilizer combination having the synergy of a mercaptan plus improved oxidative stability.
It is still another object of this invention to provide latent mercaptans as intermediates for the preparation of anti-oxidants, anti-microbial agents, photostabilizers, and primary heat stabilizers.
These and other objects of the invention which will become apparent from the following description are achieved by incorporating into a polymeric composition containing a polymer normally susceptible to heat-induced deterioration a blocked mercaptan which degrades during processing of the composition at an elevated temperature to liberate a free mercaptan. The latent mercaptan may act as the sole heat stabilizer but the free mercaptan may also synergize the activity of other heat stabilizers in the composition. Other products of the degradation of the blocked mercaptan are believed to include carbocations of the blocking moiety which are stabilized by a molecular structure in which the electron deficiency is shared by several groups. Resonance stabilization and neighboring group stabilization are two of the possible mechanisms by which the carbocations may be stabilized. The carbocations act as intermediates in the formation of stable compounds early in the hot processing of halogen-containing polymers. Although such mechanisms and the resultant carbocations are believed to be an impetus for the liberation of the active free mercaptan, this invention is in no way limited by the foregoing attempt to explain the working of the invention. Those skilled in the art will see the resonance stabilization and neighboring group stabilization that are possible in the following structures of the blocked mercaptan; other mechanisms may be at work in other blocked mercaptans represented by these structures that also liberate an active free mercaptan upon thermal and/or chemical degradation during processing of polymeric compositions containing such blocked mercaptans. For the purposes of this invention, the terms xe2x80x9cblocked mercaptanxe2x80x9d and xe2x80x9clatent mercaptanxe2x80x9d are used interchangeably to mean a thioether which degrades during processing of the composition at an elevated temperature to liberate a free mercaptan.
The stabilizer compositions of the present invention may comprise a metal-based stabilizer and such a latent mercaptan or mixture of latent mercaptans.
As used herein: the terms xe2x80x9cgroupxe2x80x9d and xe2x80x9cradicalxe2x80x9d are used interchangeably, a mono-valent radical has but one valence available for combining with another radical whereas a di-valent radical may combine with two other radicals; the term alkyl represents monovalent straight or branched chain hydrocarbon radicals containing, for example, 1 to 20 carbon atoms; the term alkylenyl represents divalent, trivalent, and tetravalent straight or branched chain hydrocarbon radicals containing, for example, 1 to 20 carbon atoms; the term aryl represents monovalent C6-C10 aromatic rings such as benzene and naphthalene; the term alkenyl represents monovalent straight or branched chain C2 to C20 hydrocarbon radicals containing at least one double bond; the term aralkyl represents a monovalent C1 to C20 hydrocarbon radical having attached thereto an aryl radical; the term alkaryl represents monovalent aryl radicals having attached thereto at least one C1-C20 alkyl group; the term cycloalkyl represents monovalent C3-C8 saturated cycloaliphatic radicals; the term cycloalkenyl represents C5-C8 cycloaliphatic radicals containing at least one double bond; the term polyalkoxy means a chain of from 2 to 6 alkoxy groups wherein the alkoxy group is ethoxy, propoxy, isopropoxy, butoxy, or the like, with or without an end group such as hydroxy, acyloxy, benzyloxy, benzoyloxy, butoxy, and tetrahydropyranyloxy; the term halogen-containing organic polymers represents halogen-containing vinyl and vinylidene-polymers or resins in which the halogen is attached directly to the carbon atoms.
Also, as used herein: an acyloxyalkyl radical originates from a carboxylic acid ester of an alkyl alcohol; the R1 radical in Formula 1 below, therefore, in the stearic acid ester of mercaptopropanol is the stearoyloxypropyl radical; likewise, the R1 radical of the oleic acid ester of mercaptopropanol, which is one the tallate esters of that alcohol, is the oleoyloxypropyl radical; the R1 radical of lauryl-3-mercaptopropionate, on the other hand, is dodecyloxy-carbonylpropyl.
The polymeric compositions of this invention contain polymers normally susceptible to heat-induced deterioration through autoxidation such as the above-noted halogen-containing polymers. The stabilizer compositions of this invention are particularly suited to impart a superior stabilization against the deteriorative effects of heat and ultra-violet light on halogen-containing organic polymers compared to that imparted by stabilizer compositions previously known in the art.
The halogen-containing organic polymers which can be stabilized according to this invention include chlorinated polyethylene having 14 to 75%, e.g. 27%, chlorine by weight, chlorinated natural and synthetic rubber, rubber hydrochloride, chlorinated polystyrene, chlorinated polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, copolymers of vinyl chloride with 1 to 90%, preferably 1 to 30%, of a copolymerizable ethylenically unsaturated material such as, for example, vinyl acetate, vinyl butyrate, vinyl benzoate, vinylidene chloride, diethyl fumarate, diethyl maleate, other alkyl fumarates and maleates, vinyl propionate, methyl acrylate, 2-ethylhexyl acrylate, butyl acrylate and other alkyl acrylates, methyl methacrylate, ethyl methacrylate, butyl methacrylate and other alkyl methacrylates, methyl alpha-chloroacrylate, styrene, trichloroethylene, vinyl ethers such as vinyl ethyl ether, vinyl chloroethyl ether and vinyl phenyl ether, vinyl ketones such as vinyl methyl ketone and vinyl phenyl ketone, 1-fluoro-2-chloroethylene, acrylonitrile, chloroacrylonitrile, allylidene diacetate and chloroallylidene diacetate. Typical copolymers include vinyl chloride-vinyl acetate (96:4 sold commercially as VYNW), vinyl chloride-vinyl acetate (87:13), vinyl chloride-vinyl acetate-maleic anhydride ((86:13:1), vinyl chloride-vinylidene chloride (95:5); vinyl chloride-diethyl fumarate (95:5), and vinyl chloride 2-ethylhexyl acrylate (80:20). In addition to the stabilizer compositions of this invention, there can also be incorporated into the halogen-containing organic polymer conventional additives such as plasticizers, pigments, fillers, dyes, ultraviolet light absorbing agents, densifying agents, biocides and the like.
Preferably, the halogen-containing organic polymer is a vinyl halide polymer, more particularly a vinyl chloride polymer. Usually, the vinyl chloride polymer is made from monomers consisting of vinyl chloride alone or a mixture of monomers comprising, preferably, at least about 70% by weight based on the total monomer weight of vinyl chloride.
FORMULA 1 is representative of the blocked mercaptans that are suitable for the purposes of this invention: 
wherein a is 0 or 1, m and n are 0 or 1; y=1 to 4; when y=1, z is 1 to 4; and when y is more than 1, z is 1; R1 is an alkyl, alkylenyl, cycloalkyl, cycloalkylenyl, aryl, alkaryl, aralkyl, aralkylenyl, hydroxyalkyl, dihydroxyalkyl, hydroxy(polyalkoxy)alkyl, alkoxyalkyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(acyloxyalkyl), alkoxy(polyalkoxy)alkyl, alkoxy(polyalkoxy)carbonylalkyl, carboxyalkyl, acyloxyalkyl, acyloxy(hydroxyalkyl), acyloxyalkoxyalkyl, acyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)alkyl, alkylenebis-(acyloxyalkyl), alkoxycarbonylalkyl, alkoxycarbonylalkylenyl, hydroxyalkoxycarbonylalkyl, hydroxy(polyalkoxy)carbonylalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkyl, mercaptoalkoxycarbonylalkylenyl, alkoxycarbonyl(amido)alkyl, alkylcarbonyloxy(polyalkoxy)carbonylalkyl, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, hydroxyaryl, mercaptoaryl or carboxyaryl radical having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, acyl, alkyl, alkylenyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, mercaptoalkyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, mercaptoaryl groups having from 1 to 22 carbon atoms; X is aryl, haloaryl, alkaryl, hydroxyaryl, dihydroxyaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom, with the option that when a is 1 and m is 1, R6 and R7 form a heterocyclic moiety in conjunction with X as nitrogen, and with the further option that when a=1 and m=0, one of R1, R3, and R5 joins with R7 and X to form a heterocyclic moiety with X as a heteroatom selected from the group consisting of oxygen and sulfur; with the proviso that z is 1 or 2 when X is aralkaryl, R6 and R7 are hydroxyl, a is 1 and m is 1, and with the further proviso that when R6xe2x89xa0hydroxyl or mercapto, z is 1.
A polymeric composition wherein the blocked mercaptan has the following structure is another embodiment of this invention: 
wherein a is 0 or 1, m and n are 0 or 1; y=1 to 4, when y=1, z is 1 to 4 when y is more than 1 z is 1; R1 is an an alkyl, alkylenyl, cycloalkyl, cycloalkylenyl, aryl, alkaryl, aralkyl, aralkylenyl, hydroxyalkyl, dihydroxyalkyl, hydroxy(polyalkoxy)alkyl, alkoxy(polyalkoxy)carbonylalkyl, alkoxyalkyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(acyloxyalkyl), alkoxy(polyalkoxy)alkyl, carboxyalkyl, acyloxyalkyl, acyloxy(hydroxyalkyl), acyloxyalkoxyalkyl, acyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)alkyl, alkylenebis-(acyloxyalkyl), alkoxycarbonylalkyl, alkoxycarbonylalkylenyl, hydroxyalkoxycarbonylalkyl, hydroxy(polyalkoxy)carbonylalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkyl, mercaptoalkoxycarbonylalkylenyl, alkoxycarbonyl(amido)alkyl, alkylcarbonyloxy(polyalkoxy)carbonylalky, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, hydroxyaryl, mercaptoaryl or carboxyaryl radical having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, alkyl, alkylenyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, mercaptoalkyl, hydroxyalkylmercaptoalkyl, mercaptoalkylenyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, arylcarbonyl, or mercaptoaryl radical having from 1 to 22 carbon atoms; when a=1, X is arylcycloalkyl or a heteroatom, and when a=0, X is aryl, haloaryl, alkaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom, with the option that when a is 1 and m is 0, one of R3 and R5 joins with R7 and X to form a heterocyclic moiety with X as a heteroatom selected from the group consisting of oxygen and sulfur, and with the further option that when a is 1 and m is 1, R6 and R7 form a heterocyclic moiety in conjunction with X as a nitrogen atom.
The mercaptan-containing organic compounds which may be converted into latent mercaptans for the purposes of this invention are well-known compounds and include alkyl mercaptans, mercapto esters, mercapto alcohols, and mercapto acids. See, for example, U.S. Pat. Nos. 3,503,924 and 3,507,827. Alkyl mercaptans having from 1 to about 200 carbon atoms and from 1 to 4 mercapto groups are suitable. Mercaptan-containing organic compounds which include R1 have structures illustrated by the following formulas: 
wherein R10 and R19 are the same or different and are 
R11 is xe2x80x94H aryl, or C1 to C18 alkyl;
R12 is cycloalkyl, cycloalkenyl or phenyl;
R13 is 
xe2x80x83with the proviso that in formula (MC2) when R12 is phenyl, R13 is xe2x80x94OH and i=0, then the xe2x80x94SH groups are on non-adjacent carbon atoms;
R14 is xe2x80x94H or a divalent group which may contain halogen, hydroxy, mercapto or alkyl substituents and which when R12 is phenyl combines with the phenyl to form a naphthalene ring;
R15 is 
R17 is xe2x80x94H, or alkyl, alkenyl, aryl, aralkyl, alkaryl, cycloalkyl, cycloalkylenyl;
R18 is arylene, C1 to C8 alkylenyl, 
wherein b is an integer from 1 to 6;
i=0 or an integer from 1 to 6 inclusive;
j=0, 1, 2 or 3; and
f=1 or 2.
Mercaptan-containing organic compounds preferred as intermediates in the preparation of the latent mercaptans of this invention are those compounds according to formula (MC1) where R11 is xe2x80x94H, R19 is xe2x80x94H, R10 is OH or 
and i=1; those compounds according to formula (MC2) where R12 is phenyl, R11 is xe2x80x94H, R13 is xe2x80x94H, R14 is xe2x80x94H, i=1, and j=1; those compounds according to formula (MC3) where R11 is xe2x80x94H, R15 is 
and i=1; those compounds according to formula (MC4) where R11 is xe2x80x94H and i=1; those compounds according to formula (MC5) where R16 is xe2x80x94C2H5 or 
R11 is xe2x80x94H and i=1; and those compounds according to formula (MC6) where R11 is xe2x80x94H and i=1.
Examples of the mercaptan-containing organic compounds described by formula (MC1) include, but are not limited to, the following compounds: 
Examples of the mercaptan-containing organic compounds described by formula (MC2) include, but are not limited to, the following compounds: 
Examples of mercaptan-containing organic compounds represented by formula (MC3) include, but are not limited to the following compounds: 
The mercaptan-containing organic compounds described by formula (MC4) are exemplified by, but are not limited to, the following: 
The mercaptan-containing organic compounds represented by formula (MC5) are exemplified by, but are not limited to, the following: 
The mercaptan-containing organic compounds represented by formula (MC6) are exemplified by, but are not limited to, the following: 
One of the advantages of this invention is that the offensive odor of the mercaptans is masked by the blocking group so that the latent mercaptan thus created may be put into a PVC composition or the like with little or no offense to the operator with the knowledge that the free mercaptan will be released as a degradation product when the treated composition is heated during the usual processing, e.g. extrusion. This advantage is also useful for the liquid polysulfides having a molecular weight of from about 1000 to about 8000 sold under the LP trademark by Morton International, Inc.
The blocking compounds are preferably those which are capable of furnishing a stabilized carbocation having a molecular structure in which the electron deficiency is shared by several groups. Resonance stabilization and neighboring group stabilization are two of the possible mechanisms by which the carbocations may be stabilized. Polarized, unsaturated compounds exemplified by 3,4-dihydropyran, 2-methoxy-3,4-dihydropyran, styrene, xcex1-methylstyrene, vinyl benzyl chloride, indene, 2-vinylpyridine, N-vinylpyrrolidone, vinyl acetate, octadecyl vinyl ether, cyclohexyl divinyl ether, ethyleneglycol monovinyl ether, allyl phenyl ether, trans-cinnamaldehyde, N-methyl-N-vinylacetamide, N-vinylcaprolactam, isoeugenol, and 2-propenylphenol are suitable. Compounds having labile halogen atoms which split off as hydrogen chloride in a condensation reaction with the mercaptan, as exemplified by triphenylmethyl chloride, benzyl chloride, and bis(chloromethyl)benzene, are also suitable. The mercaptan may also be blocked by condensation with an aldehyde such as butyraldehyde or with a benzyl alcohol such as benzene dimethanol. A preferred blocking agent is 2-hydroxybenzyl alcohol, a well known intermediate in the perfume, agricultural, and plastics industries.
In general, the procedure for adding the mercapto group of a free mercaptan across the double bonds of polarized, unsaturated compounds is:
To a stirred mixture of the mercaptan, acid catalyst, and optionally, a small percentage of antioxidant to inhibit radical reactions, under nitrogen atmosphere is added dropwise the polarized, unsaturated compound, either neat or in solution, while maintaining the temperature between 100-70xc2x0 C. The mixture or solution is then heated for between 1 to 6 hours at 35xc2x0-70xc2x0 C. and conversion to product is monitored by gas chromatography and iodine titration for SH. The acid catalyst is removed by an alkaline wash and the resulting product is dried with magnesium sulfate and filtered. The solvent, if required, is removed under reduced pressure at  less than 50xc2x0 C. to yield the latent mercaptan. This generalized procedure is referred to hereinafter as Procedure A.
In accordance with Procedure A, for example, mercaptoethanol is added across the double bond of N-vinylcaprolactam to yield N-2-hydroxyethylthioethylcaprolactam. Mercaptoethyldecanoate (or mercaptoethylcaproate) reacts with 3,4-dihydropyran in that procedure to give 2-S-(tetrahydropyranyl)thioethyldecanoate. Bis(hydroxyethylthioethyl)cyclohexyl ether is made from the mercaptoethanol and cyclohexyl di-vinyl ether. In like manner, the corresponding caprate, oleate, and tallate esters form the corresponding cyclohexyl ethers. Also, indene is converted by the addition of the mercaptoethanol to 2H-dihydroindenylthio-ethanol.
A generalized procedure for the condensation of a free mercaptan with a labile halogen-containing compound is as follows:
To a stirred mixture of the mercaptan and halogen-containing compound under nitrogen atmosphere is added dropwise a solution of sodium methoxide in methanol while maintaining the temperature below 50xc2x0 C. Optionally, the reaction is allowed to proceed without the addition of a base source and the liberated hydrogen chloride is removed by nitrogen gas sweep and neutralized with the use of an external acid scrubber. The mixture or solution is then heated for between 2 to 24 hours at 50xc2x0-70xc2x0 C. and conversion to product is monitored by gas chromatography and iodine titration for %SH. The product is then neutralized, washed with water, dried with magnesium sulfate, and filtered. The solvent, if required, is removed under reduced pressure at  less than 50xc2x0 C. to yield the latent mercaptan. This generalized procedure is referred to hereinafter as Procedure B.
A generalized procedure for the condensation of a free mercaptan with a labile hydroxyl-containing compound is as follows:
To a stirred solution of the mercaptan, acid catalyst, and solvent under nitrogen atmosphere is added the hydroxy-containing compound either neat or in solution while maintaining the temperature  less than 45xc2x0 C. The solution is then heated to 45xc2x0-75xc2x0C. for between 1 to 10 hours and conversion to product is monitored by gas chromatography and iodine titration for %SH. Optionally, an azeotropic solvent is chosen for removal of reaction water by an appropriate means at reflux temperatures, typically 60xc2x0-120xc2x0 C. Completion of reaction is achieved after the theory amount of water has been collected. The acid catalyst is removed by alkaline wash and the resulting solution is dried with magnesium sulfate and filtered. The solvent is removed under reduced pressure at  less than 55xc2x0 C. to yield the latent mercaptan. This procedure is referred to hereinafter as Procedure C.
For example, 2-hydroxybenzyl alcohol condenses with mercaptoethanol in accordance with Procedure C to form 1-(2-hydroxyphenyl)-1-S-(2-hydroxyethylthio)methane.
A generalized procedure for the reaction of a free mercaptan with a glycidyl ether is as follows:
To a stirred mixture of the mercaptan and acid catalyst under nitrogen atmosphere is added the glycidyl ether, either neat or in solution, while maintaining the temperature between 25xc2x0-60xc2x0C. The mixture or solution is then heated to between 50xc2x0-75xc2x0 C. for a period of 1 to 6 hours and conversion to product is monitored by gas chromatography and iodine titration for %SH. The acid catalyst is removed by alkaline wash, the resulting product is dried with magnesium sulfate, and filtered. The solvent, if required, is removed under reduced pressure at  less than 55xc2x0 C. to yield the latent mercaptan. For example, the reaction between mercaptoethanol and glycidyl neodecanoate gives C9H19C(xe2x95x90O)OCH2CH(OH)CH2SCH2CH2OH. This procedure is referred to hereinafter as Procedure D.
A generalized procedure for the condensation of a free mercaptan with an aldehyde is as follows:
To a stirred solution of the mercaptan, acid catalyst, and azeotropic solvent under nitrogen atmosphere is added the aldehyde with heating to reflux, typically between 65xc2x0-120xc2x0 C., for removal of reaction water. Completion of reaction is achieved after the theory amount of water has been collected.
Optionally, to a stirred solution of mercaptan, aldehyde, and ether is added BF3-etherate dropwise under reflux conditions. The solution is refluxed for between 1 to 6 hours and conversion to product is monitored by gas chromatography. The acid catalyst is removed by alkaline wash, the solution is dried with magnesium sulfate and filtered. The solvent is removed under reduced pressure at  less than 65xc2x0 C. to yield the latent mercaptan. This generalized procedure is referred to hereinafter as Procedure E.
Examples of the blocked mercaptans of this invention include compounds having the following formulas, as each relates to FORMULA 1: 
a=1, m=1, n=0; y=1, z is 1; X is nitrogen, R6 and R7 are joined to form xe2x80x94CH2-CH2xe2x80x94CH2xe2x80x94Cxe2x95x90(O)xe2x80x94; R4 is hydrogen; R5 is methyl; and R1 is hydroxyethyl. 
a=1, m=1, n=0; y=1, z is 1; X is nitrogen, R6 is acetyl, R7 is methyl, R5 is methyl, R4 is hydrogen, and R1 is hydroxyethyl. 
a=1, m=0, n=0; y=1, z is 1; X is oxygen, R5 and R7 are joined to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R4 is hydrogen, and R1 is hydroxyethyl. 
a=1, m 0, n=1, y=1, z=1; X is oxygen, R3 and R7 join to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R2, R4 and R5 are hydrogen, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=1; X is oxygen, R5 and R7 join to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R4 is hydrogen, and R1 is 2-ethoxytetrahydropyranyl. 
a=1, m=0, n=0, y=1, z=1; X is oxygen, R5 and R7 join to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R4 is hydrogen, and R1 is 3-ethoxytetrahydropyranyl. 
a=1, m=0, n=1, y=1, z=1; X is oxygen, R3 and R7 join to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R2, R4 and R5 are hydrogen, and R1 is 2-ethoxytetrahydropyranyl. 
a=1, m=0, n=1, y=1, z=1; X is oxygen, R3 and R7 join to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R1, R4 and R5 are hydrogen, and R1 is 3-ethoxytetrahydropyranyl. 
a=0, m=0, n=0, y=1, z=1; X is phenyl, R4 is methyl, R5 is hydrogen, and R1 is hydroxyethyl. 
a=0, m=0, n=1, y=1, z=1, X is phenyl, R2, R3, R4, and R5 are hydrogen, and R1 is hydroxyethyl. 
a=0, m=0, n=0, z=1; y=1, X is phenyl, R4 and R5 are hydrogen, and R1 is hydroxyethyl. 
a=1, m 0, n=0, y=1, z=1; X is phenyl, R4 and R5 are hydrogen, R7 is o-hydroxy, and R1 is hydroxyethyl. 
a 0, m=0, n=0, y=1, z=1; X is phenyl, R4 and R5 are hydrogen, and R1 is mercaptoethoxycarbonylmethyl. 
a=1, m=0, n=1, y=1, z=1; X is oxygen, R2, R4 and R5 are hydrogen, R3 is methyl, R7 is phenyl, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=1; X is oxygen, R7 and R1 are joined to form an ethylenyl radical, R4 is hydrogen, and R5 is propyl. 
a=0, m=1, n=1, y=1, z=1; X is oxygen, R2, R3, R6 and R4 are hydrogen, R5 is 2-methyleneoxytolyl, and R1 is hydroxyethyl. 
a=1, m=0, n=1, y=1, z=1; X is oxygen, R2, R3, R4 and R7 are hydrogen, R5 is butoxymethyl, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=1; X is phenyl, R4 is hydrogen, R5 is ethyl, R7 is o-hydroxy, and R1 is hydroxyethyl. 
a=1, m=0, n=1, y=1, z=1; X is phenyl, R3, R4 and R5 are hydrogen, R2 is methyl, R7 is o-hydroxy, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=2; X is phenyl, R4 is hydrogen, R5 is ethyl, R7 is o-hydroxy, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=1; X is m-methoxyphenyl, R4 is hydrogen, R5 is ethyl, R7 is p-hydroxy, and R1 is hydroxyethyl. 
a=0, m=0, n=0, y=1, z=2; X is tetrachlorophenyl, R4 and R5 are hydrogen, and R1 is hydroxyethyl. 
a=1, m=0, n=0, y=1, z=1; X is o,p-dihydroxyphenyl, R7 is mphenylcarbonyl, R4 is hydrogen, R5 is xe2x80x94CH2CH3, and R1 is hydroxyethyl. 
a=1, m=0, n=0; y=1, z is 1; X is oxygen, R5 and R7 are joined to form xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94; R4 is hydrogen, and R1 is decanoyloxyethyl. 
a=1, m=0, n=0; y=1, z is 1; X is p-hydroxyphenyl, R4 and R5 are hydrogen, R7 is m-methoxy, and R1 is hydroxyethyl.
As stated above, the stabilizer compositions of the present invention comprise a latent mercaptan as the sole heat stabilizer or in a system comprising a metal-based stabilizer, an organic-based stabilizer, or a hydrotalcite-based stabilizer in admixture with the latent mercaptan. Metal-based stabilizers are defined for the purposes of this invention as metal salt stabilizers and organometallic stabilizers. The metal salt stabilizers are exemplified by barium, strontium, calcium, cadmium, zinc, lead, tin, magnesium, cobalt, nickel, titanium, antimony, and aluminum salts of phenols, aromatic carboxylic acids, fatty acids, epoxidized fatty acids, oxalic acid, carbonic acid, sulfuric acid, and phosphoric acid. Calcium stearate, calcium 2-ethyl-hexeate, calcium octoate, calcium oleate, calcium ricin-oleate, calcium myristate, calcium palmitate, calcium laurate, barium laurate, barium stearate, barium di(nonylphenolate), magnesium stearate, zinc stearate, zinc octoate, cadmium laurate, cadmium octoate, cadmium stearate, sodium stearate and other Group I and II metal soaps are examples of suitable salts. Other metal salts such as lead stearate, hydrotalcite, aluminum stearate, etc, can be used. Metal salt stabilizers may constitute from about 0.1 to about 10%, preferably 0.1-5% by weight of the halogen containing resin.
Conventional organometallic stabilizers include the organotin carboxylates and mercaptides. Such materials include butyltin tris dodecyl mercaptide, dibutyltin dilaurate, dibutyltin didodecyl mercaptide, dianhydride tris dibutylstannane diol, dihydrocarbontin salts of carboxy mercaptals such as those set forth in Hechenbleikner et al. (U.S. Pat. No. 3,078,290). There can be included any of the vinyl chloride resin stabilizers set forth in Salyer (U.S. Pat. No. 2,985,617).
As an example of a system involving an organic-based stabilizer, a combination of a latent mercaptan and an N-substituted maleimide has been found to be synergistic in the stabilization of a flexible PVC formulation.
The stabilizer compositions of this invention comprise from about 10% to about 100%, preferably from about 35% to about 85%, by weight of one or more latent mercaptans, based on the total weight of the stabilizer composition, the balance comprising the metal-based, organic-based, or hydrotalcite-based stabilizer. Preferably, the stabilizer compositions of this invention comprise a mono-organotin compound or mixture of mono-organotin compounds, and, optionally, a diorganotin compound or mixture of diorganotin compounds or mixtures of mono-organotin and diorganotin compounds. Thus, when no diorganotin compound or mixture of diorganotin compounds is employed in the preferred stabilizer of this invention, the mono-organotin compounds will comprise from about 10% to about 90% by weight, preferably about 15% to about 65% by weight of the total weight of the stabilizer composition. When it is desirable to utilize a diorganotin compound or mixture of diorganotin compounds in the practice of this invention, said diorganotin compound or mixture of diorganotin compounds may comprise from about 0.05% to about 75%, by weight, preferably from about 0.05% to about 35% by weight of the total weight of the stabilizer composition.
The mono-organotin compounds useful in the compositions of this invention contain one or more tetravalent tin atoms each of which have one direct tin to carbon bond and have structures selected from the following formulas: 
wherein Z and Zxe2x80x2 are the same or different and are selected from 
xe2x80x83with the proviso that in formula (E) when z=1 and in formulas (C) and (D) at least one Z or Zxe2x80x3 is xe2x80x94SR32;
Y is 
W and W1 are the same or different and are oxygen or sulfur; R30 and R31 are the same or different and are selected from alkyl, aryl, alkenyl, aralkyl, alkaryl, cycloalkyl, cycloalkenyl, 
R32 is alkyl, alkenyl, aryl, aralkyl, cycloalkyl, cycloalkenyl, 
R33 is alkyl, alkenyl, aryl, aralkyl, alkaryl, cycloalkyl, or cycloalkenyl;
R34 is alkylene of at least 2 carbon atoms, arylene, alkenylene of at least 2 carbon atoms, cycloalkylene, or cycloalkenylene;
R35 is alkylene, arylene, alkenylene of at least 2 carbon atoms, cycloalkylene, or cycloalkenylene;
R36 is R34;
R37 is nothing or R35;
R38 is C1 to C4 alkylenyl;
R39 is xe2x80x94H or a monovalent C1 to C20 hydrocarbon radical;
R40 and R41 are the same or different and are each C1 to C32 alkyl or C1 to C20 alkoxy;
R42 is xe2x80x94H or R33;
q=0 or an integer from 1 to 4 inclusive;
v=an integer from 1 to 8 inclusive; and
w=0, 1 or 2, x=0 or 1, z=0 or 1 with the proviso that when x=0 then z=1, when x=1 then z=0 and w=1, when w=2 then x=0 and z=1, and when w=0 then x=0, z=1 and Y is xe2x80x94Wxe2x80x94R34xe2x80x94W1xe2x80x94 or 
The preferred mono-organotin compounds useful in this invention are those compounds according to formula (A) where R30 is methyl, outyl or octyl and W is sulfur; those compounds according to formula (B) where R31 is methyl or butyl, W is sulfur, Z is xe2x80x94SR32 where R32 is 
those compounds according to formula (C) where R30 is methyl or butyl, Z is xe2x80x94SR32 where R32 is 
those compounds according to formula (D) where R30 is methyl, Z is xe2x80x94SR32 where R32 is 
R31 is methyl, Zxe2x80x2 is xe2x80x94SR32 where R32 is 
Y is xe2x80x94Sxe2x80x94, and q=0; and those compounds according to formula (E) where R30 is methyl, Z is xe2x80x94SR32 where R32 is 
R31 is methyl, Zxe2x80x2 is xe2x80x94SR32 where R32 is 
Y is xe2x80x94Sxe2x80x94, W=1, x=0, and z=1.
Examples of mono-organotin compounds which are useful in this invention include, but are not limited to, those illustrated in Tables 1-4 below. Thus, representative of the mono-organotin compounds described by formulas (A) and (B) are those illustrated in Table 1 below.
Examples of mono-organotin compounds represented by formula (C) are illustrated in Table 2 below.
The mono-organotin compounds illustrated in Table 3 below are representative of compounds described in formula (D).
The mono-organotin compound illustrated in Table 4 below is representative of compounds described by formula (E).
As used in Tables 1-3 above, and throughout this specification, the radicals xe2x80x94C4H9, xe2x80x94C8H17, xe2x80x94C12H25, xe2x80x94C9H19 and xe2x80x94C10H21 represent n-butyl, n-octyl, n-dodecyl, n-nonyl and n-decyl respectively.
The carboxyl radicals 
are derived from oleic acid, scearic acid, n-octanoic acid, lauric acid, and pelargonic acid respectively. Likewise, the radicals xe2x80x94OC13H27, xe2x80x94OC18H37, and xe2x80x94OC8H17, are derived from tridecanol, stearyl alcohol and iso-octanol, respectively.
The diorganotin compounds useful in the practice of this invention contain one or more tetravalent tin atoms, at least one of which has direct bonds to two carbon atoms and have structure selected from the following formulas: 
wherein R30, R31, W, Z, Z1, Y, w and z are as previously defined; n=0, 1 or 2, p=0, 1 or 2 with proviso that n+p=2, and m=1 to 5;
y=1 or 2, y=2 with the proviso that when w=0 then Y is xe2x80x94Wxe2x80x94R34xe2x80x94W1xe2x80x94, or 
and in formula (J) when z=1 and in formulas (G) and (H) at least one Z or Z1 is xe2x80x94SR32.
The preferred diorganotin compounds used in the practice of this invention are those compounds according to formula (F) where R is methyl or butyl, R31 is methyl or butyl and W is sulfur; those compounds according to formula (G) where R is methyl or butyl, R31 is methyl or butyl, Z is xe2x80x94SR32 where R32 is 
those compounds according to formula (H) where R30 is methyl or butyl, R31 is methyl or butyl, Y is xe2x80x94Sxe2x80x94, Z is xe2x80x94SR32 where R32 is 
m=1, n=2 and p=0; and those compounds according to formula (J) where R30 is methyl or butyl, R31 is methyl or butyl, Z is xe2x80x94SR32 and R32 is 
Y is xe2x80x94Sxe2x80x94, w=1, y=1 and z=1.
Examples of diorganotin compounds according to formula (F) include, but are not limited to, the compounds illustrated in Table 5 below.
Examples of diorganotin compounds according to formula G include, but are not limited to, the compounds in Table 6 below.
Examples of diorganotin compounds according to formula (H) include, but are not limited to, the compounds in Table 7 below.
Examples of diorganotin compounds according to formula (J) include, but are not limited to, the compounds in Table 8 below.
The mono-organotin compounds and diorganotin compounds useful in the compositions of this invention may be prepared by methods well-known in the art such as the reaction of a mono- or dialkyltin chloride with a mercaptoalkyl carboxylate or an alkyl thioglycolate in the presence of a base to scavenge hydrogen chloride. Methyltin trichloride, dimethyltin dichloride, butyltin trichloride, dibutyltin dichloride, ethylhexyltin trichloride, and dioctyltin dichloride are examples of organotin halides that are suitable for the preparation of useful stabilizers for this invention. See for example, U.S. Pat. Nos. 3,565,930, 3,869,487, 3,979,359, 4,118,371, 4,134,878 and 4,183,846 all of which are incorporated herein by reference.
Monosulfides and/or polysulfides of the mercaptoalkyl carboxylates and alkyl thioglycolates are also suitable as metal based stabilizers in the compositions of this invention for improving the resistance of halogen-containing polymers to deterioration when heated to 350xc2x0 F. (177xc2x0 C.) during processing. Polysulfides are mixtures of compounds having from 2 to 10 or more sulfur atoms linked together but compounds having from 2 to 4 sulfur atoms are preferred along with the monosulfides. Said sulfides are made by heating stoichiometric quantities of a mercaptoalkyl ester or alkylthiocarboxylate and an organotin chloride in water and ammonium hydroxide to about 30xc2x0 C. (86xc2x0 F.), slowly adding an alkali metal mono- or polysulfide, and heating the reaction mixture further to about 45xc2x0 C. before separating the product from said mixture. The sulfides may be described as a blend of the reaction products which are believed to include the monosulfides and polysulfides of the mercaptoalkylesters and thioglycolates. Said sulfides contain from about 10 to about 42% by weight of tin and from about 8 to about 42% by weight cf sulfur. The sulfides of the mercaptoalkyl esters and their preparation are described in U.S. Pat. No. 4,062,881. These sulfides are believed to include the bis[(monoorganotin)bis(mercapto-alkylcarboxylate)]monosulfides and polysulfides, and bis[(diorganotin)mono(mercaptoalkyl-carboxylate)]monosulfides and polysulfides, and products which arise during equilibrium reactions among said mono- and polysulfides. The chemical and patent literature contain numerous examples demonstrating that members of different classes of organotin compounds may react with one another under certain conditions to yield products containing one or more tin atoms wherein at least a portion of the tin atoms are bonded to different combinations of radicals than they were before being mixed together.
Conventional non-metallic stabilizers and antioxidants can also be included in the stabilizer compositions of the present invention to assist in improving the properties of the halogen containing resin. Thus, there can be included 0.01-10%, preferably 0.1-5% based on the resin of sulfur containing compounds such as dilauryl-thiodipropionate, distearyl 3,3xe2x80x2-thiodipropionate, dicyclohexyl-3,3-thiodipropionate, dioleyl-3,3xe2x80x2-thiodipropionate, dibenzyl-3,3xe2x80x2-thiodipropionate, didecyl-3,3xe2x80x2-thiodipropionate, dibenzyl-3,3xe2x80x2-thiodipropionate, diethyl-3,3xe2x80x2-thiopropionate, lauryl ester of 3-methylmercaptopropionic acid, lauryl ester of 3-butylmercaptopropionic acid, lauryl ester of 3-lauryl mercaptopropionic acid, and phenyl ester of 3-octyl mercaptopropionic acid.
Phenolic antioxidants can also be added in an amount of 0.01-10%, preferably 0.1-5% of the halogen-containing resin. Examples of such antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, propyl gallate, 4,4xe2x80x2-thiobis(6-t-butyl-m-cresol), 4,4xe2x80x2-cyclohexylidenediphenol, 2,5-di-t-amyl hydroquinone, 4,4xe2x80x2-butylidene bis(6-t-butyl-m-cresol), hydroquinone monobenzyl ether, 2,2xe2x80x2-methylene-bis(4-methyl-6-t-butyl phenol), 2,6-butyl-4-decyloxy phenol, 2-t-butyl-4-dodecyloxy phenol, 2-t-butyl-4-dodecyloxy phenol, 2-t-butyl-4-octadecyloxy phenol, 4,4xe2x80x2-methylene-bis(2,6-di-t-butyl phenol), p-amino phenol, N-lauryloxy-p-amino phenol, 4,4xe2x80x2-thiobis(3-methyl-6-t-butyl phenol), bis[o-(1,1,3,3-tetramethyl butyl)phenol]sulfide, 4-acetyl-xcex2-resorcylic acid, A-stage p-t-butylphenolformaldehyde resin, 4-dodecyloxy-2-hydroxybenzophenone, 3-hydroxy-4-(phenylcarbonyl)phenyl palmitate, n-dodecyl ester of 3-hydroxy-4-(phenylcarbonyl)phenoxyacetic acid, and t-butyl phenol.
The use of epoxy compounds in an amount of 0.01-5% in the polymer compositions is also valuable. Examples of such epoxy compounds include epoxidized soya bean oil, epoxidized lard oil, epoxidized olive oil, epoxidized linseed oil, epoxidized castor oil, epoxidized peanut oil, epoxidized corn oil, epoxidized tung oil, epoxidized cottonseed oil, epichlorhydrin/bis-phenol A resins, phenoxy-propylene oxide, butoxypropylene oxide, epoxidized neopentylene oleate, glycidyl epoxystearate, epoxidized xcex1-olefins, epoxidized glycidyl soyate, dicyclopentadiene dioxide, epoxidized butyl toluate, styrene oxide, dipentene dioxide, glycidol, vinyl cyclo-hexene dioxide, glycidyl ether of resorcinol, glycidol ether of hydroquinone, glycidyl ether of 1,5-dihyroxynaphthalene, epoxidized linseed oil fatty acids, allyl glycidyl ether, butyl glycidyl ether, cyclohexane oxide, 4-(2,3-epoxypropoxy)acetophenone, mesityl oxide epoxide, 2-ethyl-3-propyl glycidamide, glycidyl ethers of glycerine, pentaerythritol and sorbitol, and 3,4-epoxycyclohexane-1,1-dimethanol bis-9,10-epoxystearate.
Likewise there can be used organic phosphites in an amount of 0.01 to 10%, preferably 0.1-5% of the halogen containing resins. The organic phosphites contain one or more, up to a total of three, aryl, alkyl, aralkyl and alkaryl groups, in any combination. The term xe2x80x9ctrialkylarylxe2x80x9d is inclusive of alkyl, aryl, alkaryl and aralkyl phosphites containing any assortment of alkyl, aryl, alkaryl and aralkyl groups. Exemplary are triphenyl phosphite, tricresyl phosphite, tri(dimethylphenyl)phosphite, tributyl phosphite, trioctyl phosphite, tridodecyl phosphite, octyl diphenyl phosphite, dioctyl phenyl phosphite, tri(octyl-phenyl)phosphite, tri(nonylphenyl)phosphita, tribenzyl phosphite, butyl dicresyl phosphite, octyl di(octyl-phenyl)phosphite, tri(2-ethyl-hexyl)phosphite, tritolyl phosphite, tri(2-cyclohexylphenyl)phosphite, tri-alpha-naphthyl phosphite, tri(phenylphenyl)phosphite, and tri(2-phenylethyl)phosphite.
Likewise there can be included polyol stabilizers for vinyl chloride resins in an amount of 0.01-10%. Thus there can be included glycerol, sorbitol, pentaerythritol and mannitol.
Nitrogen containing stabilizers such as dicyandiamide, melamine, urea, formoguanamine, dimethyl hydantoin, guanidine, thiourea, 2-phenylindoles, aminocrotonates, N-alkyl and N-phenyl substituted maleimides, wherein the alkyl group has from 1 to 4 carbon atoms, and the like also can be included in amounts of 0.1-10%. There can even be included conventional lubricants for vinyl chloride resins such as low molecular weight polyethylene, i.e. polyethylene wax, fatty acid amides, e.g. lauramide and stear-amide, bisamides, e.g. decamethylene, bis amide, and fatty acid esters, e.g. butyl stearate, glyceryl stearate, linseed oil, palm oil, decyloleate, corn oil, cottonseed oil, hydrogenated cottonseed oil, etc.
The stabilizer compositions of this invention may be prepared by blending the components thereof in any convenient manner which produces a homogeneous mixture, such as by shaking or stirring in a container. Likewise, the stabilized compositions of this invention can be incorporated in the halogen-containing organic polymer by admixing the stabilizer composition and polymer, such as, for example, in an appropriate mill or mixer or by any other of the well-known methods which provide uniform distribution of the stabilizer throughout the polymer.
The stabilizer compositions of this invention are employed in an amount sufficient to impart the desired resistance to heat deterioration to halogen-containing organic polymers. It will be readily apparent to one of ordinary skill in the art, that the precise amount of stabilizer composition used will depend upon several factors, including, but not limited to, the particular halogen-containing organic polymer employed, the temperature to which the polymer will be subjected, and the possible presence of other stabilizing compounds. In general, the more severe the conditions to which the halogen-containing organic polymer is sub-jected, and the longer the term required for resisting degradation, the greater will be the amount of stabilizer composition required. Generally, as little as about 0.20 part by weight of the stabilizer composition per hundred parts by weight of halogen-containing organic polymer will be effective. While there is no critical upper limit to the amount of stabilizer composition which can be employed, amounts in excess of about 10 parts by weight of halogen-containing organic polymer do not give an increase in effectiveness commensurate with the additional amount of stabilizer employed.